answer
0.54
explanation
since student A and student B are independent of each other, we multiply their individual probabilities to get the probability of both solving the problem
A * B
= 0.9 * 0.6
= 0.54
there is a 0.54 probability that both will solve the problem
since the selling price is 89.83 and the cost of is 76, the tax amount is 89.83 - 76 = 13.83.
if we take 76 to be the 100%, what is 13.83 off of it in percentage?
Mean = 133.9
then calculate the z value
with z value you will find out the p value on a table.
if the p value is below .05 reject the null hypotheses